gluCylinder draws a cylinder oriented along the z axis.
The base of the cylinder is placed at z = 0, and the top at $ z ~=~ "height"
$. Like a sphere, a cylinder is subdivided around the z axis into slices,
and along the z axis into stacks.

Note that if top is set to 0.0, this routine
generates a cone.

If the orientation is set to GLU_OUTSIDE (with gluQuadricOrientation),
then any generated normals point away from the z axis. Otherwise, they point
toward the z axis.

If texturing is turned on (with gluQuadricTexture),
then texture coordinates are generated so that t ranges linearly from
0.0 at z = 0 to 1.0 at z = height, and s ranges from 0.0 at the +y axis,
to 0.25 at the +x axis, to 0.5 at the -y axis, to 0.75 at the -x axis, and
back to 1.0 at the +y axis.